Feed distributor for screening machine

ABSTRACT

A distributor for directing an incoming feed stream uniformly to the different screen areas of a screening machine. The stream falls on a rotating, canted thrower which throws or slings the material outwardly along a rotating circular path, so that it falls between vanes on a roof over the screen. The vanes are angulated to direct the material over the edge of the roof, so that it falls at substantially uniform rates to different areas of the screen below.

United States Patent 91 Lower FEED DISTRIBUTOR FOR SCREENING MACHINE Inventor: William Lower, Cincinnati, Ohio The Orville Simpson Company, Cincinnati, Ohio Filed: Dec. 8, 1972 Appl. No.: 313,544

Assignees US. Cl. 209/254 Int. Cl 1307b 1/46 Field of Search 209/254, 150, 243, 315,,

References Cited UNITED STATES PATENTS Woodbury Ham bric Heller 210/405 Cover 209/254 [451 June 25, 1974 2,796,237 6/1957 Nettel 55/474 X 3,416,660 12/1968 Larsson 209/317 X FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Frank W. Lutter Assistant ExaminerRalph J. Hill Attorney, Agent, or FirmWood, Herron & Evans [5 7] ABSTRACT A distributor for directing an incoming feed stream uniformly to the different screen areas of a screening machine. The stream falls on a rotating, canted thrower which throws or slings the material outwardly along a rotating circular path, so that it falls between vanes on a roof over the screen. The vanes are angulated to direct the material over the edge of the roof, so that it falls at substantially uniform rates to different areas of the screen below.

8 Claims, 4 Drawing Figures 9/1960 France 209/254' 1 FEED DISTRIBUTOR FOR'SCREENING MACHINE This invention relates to screening machinery of the type used to assort particulate or chip materials of different sizes, and to separate solid-liquid mixtures. More particularly, the invention relates to an apparatus and method for distributing the incoming feed material over the area of the screen so that the feed is distributed uniformly over the various sections or regions of the screen.

The feed distributor of this invention is useful with high capacity chip screeners and it is described hereinafter with primary reference to such apparatus, although it can be used with other types of screeners.

A high capacity chip screener may handle a throughput of as much as 23,000 cubic feet of loose chips per hour, or more. In one such machine, by way of example, the incoming material is directed onto a screen or perforated plate having apertures through which material smaller than a certain limiting maximum size can pass, while the larger chips are retained on the screen and are taken off separately. A second separation is made on a lower screen or deck having smaller apertures. The screen or screens are mounted in a frame which is suspended on cables from an overhead framework, for vibrating movement. The frame is vibrated or gyrated by a driven eccentric weight. The screens used in such machines are often rectangular, and are quite large; overall screen areas of by feet are now being used.

The feed distributor of this invention is especially useful with screeners which have screens that are highly asymmetrical about their center points, such as rectangular screens. Incoming material discharged over the center of a rectangular screen will not be distributed uniformly over the entire screen area by the vibratory forces, and the screen comers will be underfed, and used inefficiently. The feed distributor is especially useful to distribute the incoming material toward such corner screen areas of a rectangular screen. However, it is also useful with a screener having a circular, regular polygonal, or other symmetrical screen shape, because the incoming material usually does not drop on the center point of the screen with accuracy or consistency, but rather tends to wander off-center due to rate of discharge variation, misalignment, clumping, vibration, and other factors.

The incoming material is usually delivered from a hopper, chute, conveyor, or cyclone, and is discharged over the screen as a rather dense or concentrated stream which must be spread over the screen area. The vibration of the screen of course assists in the spreading action, but if the incoming material were permitted to fall directly onto the screen, without additional distribution or spread out, it would tend to collect unevenly on a relatively small screen area at a chip depth greater than desired for high efficiency. This of course would result in inefficient utilization of the screen, and a lower rate of separation.

It is known in the art to provide means for distributing incoming material over a screen. The use of a distributor hood, cone, or roof is know, as shown in Simpson U.S. Pat. No. 2,946,440. An l869 patent to Foster, U.S. Pat. No. 95,674, shows the provision of angulated vanes or baffles to deflect and spread an incoming feed stream. In Alpaugh U.S. Pat. No. 489,552, a rotating cone with radially arranged spikes on it is used to break up-or crumble flow, which falls to a screen below the cone. Use of fixed vanes on a conical roof is shown in Woodbury U.S. Pat. No. 580,030, to equalize the distribution of flow to a concentrating belt. Minogue U.S. Pat. No. 2,012,726 shows a screener wherein feed is delivered'through a pipe onto a rotating conical spinner, which throws the material outwardly between vanes that rotate with the spinner. The vanes provide a contrifugal impeller action by slinging the feed material outwardly to a fan chamber between a second set of vanes, wherein it is acted upon by an upwardly rising airstream.

Such prior feed distributors achieve most uniform distribution only when the incoming material is a stream which is more or less constant in direction. In practice, however, as previously pointed out, the feed stream usually wanders officenter so that it is not distributed as uniformly as might be desired.

It has therefore been a principal objective .of this invention to provide a feed distributor which can accommodate or accept an incoming stream that is not constant in direction or position, so that regardless of such variations the stream is distributed uniformly to the screen served by the distributor.

Apparatus in accordance with this invention includes a thrower which is canted or disposed at an angle with respect to the horizontal. Drive means rotates the thrower about a generally vertical axis. The function of the thrower, which preferably is a tilted flat plate, is to deflect the incoming material outwardly in a rotating circular path. The thrower is positioned above a roof disposed over the central part of the screen. The roof has a peak which is in alignment with the axis about which the thrower rotates. The roof extends outwardly and downwardly from the peak, toward an outer edge which is spaced inwardly of and above the outer margin of the screen itself. A series of vanes is mounted on the roof around the rotatable plate, directed angularly outwardly from the axis of plate rotation. The vanes are positioned on the roof to direct material slung outwardly by the thrower over the edge of the roof to the marginal areas of the screen, at substantially uniform rates of flow per unit screen area served by the distributor.

The invention can best be further described by reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a chip screener provided with a feed distributor in accordance with a preferred form of the invention;

FIG. 2 is a horizontal section taken on line 22 of FIG. 1; 4

FIG. 3 is a vertical section taken on line 3--3 of FIG. 2; and

FIG. 4 is a section generally similar to FIG. 3, but is of a slightly modified embodiment, and shows the thrower plate rotated from the position in which it is shown in FIG. 3.

In the drawings, the distributor is shown as used in conjunction with a chip screener which is designated generally by 10. The screener is suspended for vibratory movement on cables or rods 11 at its comers, from the overhead structure of a frame 12.

The screener 10 itself does not comprise the invention, and may be of known type. The particular screener illustrated for purpose of exemplification includes a generally rectangular screen box 15 which mounts an upper screen deck 16 and a lower screen deck 17 (see FIGS. 3 and 4). In the embodiment shown, screen deck 16 is rectangular and is comprised of six separate sections, designated at l6af. The six sections of screen deck 16 are physically discrete, for separate removal and change. However, this is not important to the invention, and the word section, as used herein in reference to the screen, includes both physically discrete screen sections as well as contiguous areas on a single screen. The sections l6a-c and l6d-f reside on the opposite side of the center line of the screen box, and are angulated downwardly toward the center so as to deliver oversize material retained on them to a central trough 20. Screen deck 17 may be of generally similar construction, and is disposed directly below deck 16.

Each screen deck 16 and 17 is supported upon frame members indicated at 18. The upper screen deck 16 has apertures which are larger than the apertures in lower screen 17, so that the larger chips will be retained on screen 16, while smaller chips will drop through and fall onto screen 17. The apertures in screen 17 are sized so that particles of a desired range are retained on screen 17, while undersized particles pass through it. A ball screen cleaner 22 may be associated with either or both of screens 16 and 17, for example as shown in Simpson US. Pat. No. 2,946,440, but this comprises no part of the invention.

While-the screener is in operation, the particles retained on screen 16 will flow downwardly to the central trough 20, and will be delivered by it to a chute 23 located below the middle of the screen. Particles passing through screen 16 but retained on screen 17 are delivered toa separate output chute 24, while undersize particles (which pass through screen 17) drop to the bottom pan 25 and are delivered to a chute 26. The chutes 23, 24 and 26 will typically be connected to various silos or collection bins by conduits not shown.

Vibratory motion is imparted to the screener by means mounted within the screen box 15. An electric motor 29 (see FIG. 2) is connected through a belt 30 and a driven pulley 31, to turn a shaft 32 having an axis which is generally vertical. The shaft is journaled in bearings 33 and 34 supported or mounted within the screen box 15. An eccentric weight 35 is mounted to shaft 32 for rotation with it, and as motor 29 drives eccentric 35, vibratory motion of the entire screen assembly is established.

A roof or distributor panel 38, preferably rectangular in plan, is mounted above screen deck 16, and covers the central (middle) part of the screen, but terminates inwardly on each side at a longitudinal edge 39 which is disposed inwardly and above the outer marginal area 40 of the screen 16. In the embodiment shown, roof 38 is in the form of an inverted V and has a peak 43 which is parallel to the two roof edges 39 and in alignment with and extending through the axis of shaft 32 (see FIG. 2).

Shaft 32 extends through an aperture at the mid point of roof peak 43, and projects above it. A thrower shown generally at 45 is mounted to shaft 32 above roof peak 43. The thrower includes a flange or bracket 46 mounted to the shaft, and a circular flat plate 47 is mounted to flange 46, at an angle with respect to horizontal (see FIG. 3). It is useful, although not necessarily required, to provide for adjustment of the angulation of plate 47 with respect to the horizontal, and for that purpose in the embodiment shown, plate 47 is hinged at 48 to one side of flange 46. On the other side of the axis of shaft 32 from hinge 48, a threaded stop 49 projects upwardly from the flange. This stop is fixed to flange 46 and is held by lock nuts 50 at the desired angle. The elevation of stop 49 can be changed, so as to change the angulation of plate 47, by adjusting the lock nuts 50. For screening wood chips, an angulation of about 7 is useful, at a rate of rotation of 200 rpm. However, the optimal speeds of rotation and angulation will be different for different materials, different screen sizes and different input flow rates. The optimum setting conditions for a given application can readily be determined by changing the rate of rotation of the shaft, as by changing the diameter of pulley 31 or by changing the motor speed, and/or by adjusting the height of stop 49.,

Incoming material to be separated is directed through a chute so as to fall upon plate 47 while the latter is being rotated. In this connection, plate 47 should be sized large enough that the incoming material will fall on it, even though the stream of material may wander about the vertical axis of shaft 32, as previously mentioned. v

A series of fixed baffles or vanes, designated generally at 56, are mounted atop roof 38 around the rotatable plate 47 of the thrower 45.,These vanes direct material that is slung or thrown between them from the ro tating plate 47, outward-toward the two edges 39, 39 of roof 38, in such pattern of flow that the material will fall from the roof onto the different screen areas l6a-f at rates which are substantially uniform for equal screen areas. In the embodiment shown, these screen sections l6a-f are of substantially equal areas, and in this case it is desirable to have equal weights of material deposited on the respective screen sections in unit time. I

From FIG. 2 it will be apparent that the various vanes 56 divide the material slung outwardly from plate 47 into six portions, which they direct downwardly and outwardly to the respective outer marginal portions 40 of the screen sections l6a-f.

One vane extends along roof peak line 43. On each side of it, a pair of vanes 57, 58 project outwardly from beneath the rotatable plate 47, subtending an angle 59 between them (see FIG. 2). Each vane 57, 58 leads to an angled portion 60 which turns generally toward the corner of the roof. The vanes 60 extend to roof support members 61 which, in the embodiment shown, lie above the side edges of the central screen sections 16b and e. Material which is slung outwardly by rotation of head plate 47 into the corner area between the roof peak 43 and a vane 57 or 58, is directed by and between those vanes toward the corresponding outer corner screen sections 16a, 0, d and f. (In the-embodiment shown, the angle 62, between the vanes 57 or 58 and the roof peak 43, is equal to the angle 59 between vanes 57, 58, because the screen surfaces fed by the vanes are of equal width and area; however in other instances these angles may differ.) What is important is that the vanes are positioned on the roof to divide the incoming material into fractions and to direct those fractions to the various screen sections such that the rate of flow of material on the screen areas are substantially equal for equal areas. It is this factor which determines the angles between the vanes, and they will depend upon screen slope and dimension and other parameters in any given machine.

It is also desirable to provide an additional vane 63, between each vane 57 or 58 and the roof peak 43. The purpose of this vane 63 is to insure that material is fed at a generally uniform rate across the entire longitudinal extent of the corner screen 16a, 0, d and f, so that material directed to those sections by the adjacent vanes 57, 60 or 58, 60 is not excessively concentrated on the screen margin 40 adjacent the roof support member 61, but also is fed toward the corner area 65 thereof (see FIG. 2). Additional vanes similar to the vane 63 may be added to produce more uniform distribution to the screen sections if needed in a particular situation. It is also contemplated that a weir 67 may be provided, adjacent the edge 39 of the roof, further to smooth out distribution (see FIG. 4). The vane 63 may also be provided with adjustable slots 68 for this purpose (see FIG. 2).

In carrying out the method according to the invention, the incoming material is delivered via conduit 55 so as to fall as a stream onto the asymmetric thrower. plate 47 while the plate is being rotated by motor 29 about the vertical axis of shaft 32. The thrower deflects essentially the entire stream of material outwardly along a radial path, which path rotates as the plate is rotated.

FIG. 3 shows the thrower deflecting the stream of incoming material along a momentary path 69 which is to the left side of center, while FIG 4 shows the thrower plate rotated 180 from the FIG. 2 position, and deflecting the incoming material on the path 69 to the right side. Thus, the material is spread out in uniform circular fashion along a resultant rotating circular path regardless of whether the incoming material falls on the plate in alignment with axis of shaft 32, or wanders off axis. The outwardly slung material is divided into angularly separate portions by and between the vanes at the roof peak 43, and the vanes 57 and 58. These vanes conduct the separated portions of the material outwardly and downwardly to the different sections l6a-f of the screen, so that the material falls on those sections at rates which are substantially uniform.

Using the apparatus shown for the separation of wood chips at a feed rate of 400 cfm, the angles 59 and 62 were set at 60. The thrower plate 47 was rotated at 200 rpm, at a 7 angulation. The feed to each screen section l6a-f approximated 67 cfm.

Having described the invention, what is claimed is:

1. Apparatus for distributing incoming material over the area of a screen in a screening machine, comprismg, a thrower angulated to deflect falling material outwardly along a radial path, said thrower being rotatable about a generally vertical axis, drive means for rotating said thrower so that said radial path rotates about said axis, 7

feed means for directing the incoming material so that it falls upon said thrower,

a roof disposed centrally above said screen, said roof extendingoutwardly and downwardly from a peak thereof toward an outer edge that is positioned above the screen,

and a series of vanes mounted on said roof around said axis and directed outwardly from said thrower, the vanes being positioned on the roof so as to direct material slung between them by rotation of said thrower about said axis to different areas of said screen at substantailly uniform rates of flow per unit screen area.

2. The apparatus of claim I wherein said roof is in the form of an inverted V having a peak which passes through said axis.

3. The apparatus of claim 2 wherein said screen is rectangular andsaid vanes divide each side of said roof into a plurality of flow areas for directing said material to different areas of said screen.

4. The apparatus of claim 3 wherein said vanes are positioned on each side of said peak to direct flow uniformly among a central part of the screen and two areas at the respective ends of the screen.

5. The apparatus of claim 1 wherein said thrower is in the form of a flat plate which is tilted at an angle "with respect to horizontal.

6. The apparatus of claim 5 which further includes means for changing the angulation of saidplate, and means for holding the plate at a desired angulation.

7. A method of distributing incoming material over the area of a screen in a screening machine, said method comprising,

directing said material to fall as a stream, deflecting essentially the entire stream outwardly along a radial path, I

simultaneously rotating the radial path of the deflected material about a vertical axis so that the material is distributed circularly,

dividing the deflected material into angularly separate portions,

and conducting the angularly separated portions outwardly and downwardly to different sections of the screen so that the material is fed to the different sections at rates per unit area which are substantially uniform.

8. The method of claim 7 wherein said material is directed to fall as a stream onto a thrower which is tilted to deflect the stream outwardly along said radial path,

and wherein said thrower is rotated about said vertical axis thereby rotating the radial path along which said stream is deflected. a: l= 

1. Apparatus for distributing incoming material over the area of a screen in a screening machine, comprising, a thrower angulated to deflect falling material outwardly along a radial path, said thrower being rotatable about a generally vertical axis, drive means for rotating said thrower so that said radial path rotates about said axis, feed means for directing the incoming material so that it falls upon said thrower, a roof disposed centrally above said screen, said roof extending outwardly and downwardly from a peak thereof toward an outer edge that is positioned above the screen, and a series of vanes mounted on said roof around said axis and directed outwardly from said thrower, the vanes being positioned on the roof so as to direct material slung between them by rotation of said thrower about said axis to different areas of said screen at substantailly uniform rates of flow per unit screen area.
 2. The apparatus of claim 1 wherein said roof is in the form of an inverted V having a peak which passes through said axis.
 3. The apparatus of claim 2 wherein said screen is rectangular and said vanes divide each side of said roof into a plurality of flow areas for directing said material to different areas of said screen.
 4. The apparatus of claim 3 wherein said vanes are positioned on each side of said peak to direct flow uniformly among a central part of the screen and two areas at the respective ends of the screen.
 5. The apparatus of claim 1 wherein said thrower is in the form of a flat plate which is tilted at an angle with respect to horizontal.
 6. The apparatus of claim 5 which further includes means for changing the angulation of said plate, and means for holding the plate at a desired angulation.
 7. A method of distributing incoming material over the area of a screen in a screening machine, said method comprising, directing said material to fall as a stream, deflecting essentially the entire stream outwardly along a radial path, simultaneously rotating the radial path of the deflected material about a vertical axis so that the material is distributed circularly, dividing the deflected material into angularly separate portions, and conducting the angularly separated portions outwardly and downwardly to different sections of the screen so that the material is fed to the different sections At rates per unit area which are substantially uniform.
 8. The method of claim 7 wherein said material is directed to fall as a stream onto a thrower which is tilted to deflect the stream outwardly along said radial path, and wherein said thrower is rotated about said vertical axis thereby rotating the radial path along which said stream is deflected. 